RFR: 84: Default bug ID format should match the JDK default

[Kevin Rushforth via github.com]

Fix for [SKARA-84](https://bugs.openjdk.java.net/browse/SKARA-84) to change the default issue pattern to require exactly 7 digits with no prefix to match `hg jcheck`.

I updated all of the tests to account for this and added new tests for now-invalid formats.

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Commits:
 - 4e819911:	84: Default bug ID format should match the JDK default

Pull request:
https://git.openjdk.java.net/skara/pull/99

Webrev:
https://webrevs.openjdk.java.net/skara/99/webrev.00

Patch:
https://git.openjdk.java.net/skara/pull/99.diff

Fetch command:
git fetch https://git.openjdk.java.net/skara pull/99/head:pull/99